In road construction, hot asphalt is usually distributed transversely across the width of an intended road pathway before being smoothed and precompacted by a road paver, e.g., with a tamper beam and/or a paving screed. Further, while the asphalt material is still hot and plastic, the new road surface is usually further compacted by road rollers following the road paver, said road rollers being configured, e.g., as tandem rollers, single-drum rollers or rubber-tired rollers. A road will reach its maximum life span only at an optimum degree of compaction. Insufficient or excessive compaction both result in a reduced durability of the road surface and thus in a reduced quality of the finished road. For road construction projects, the operators of the road rollers generally define rolling patterns adapted to the asphalt layer to be compacted, including the sequence and the number of passages to be performed, in order to achieve a compaction of the asphalt layer that is as even as possible. Just how even the compaction of the entire road surface ultimately turns out depends largely on how strictly the operators of the road rollers adhere to the provided rolling pattern. The objective of these rolling patterns is to compact the road surface as evenly as possible over its width and length.
Adherence to the rolling pattern is, however, not the only aspect with respect to which the road roller operators need to be careful. For example, they also need to coordinate with other rollers and keep an eye on the progress of the road paver. Moreover, these rollers need to be guided particularly precisely in the edge region of the asphalt layer, since they are also supposed to create a straight, sharp road edge by means of, e.g., pressure rollers attached to the sides of the road rollers. It is thus possible that certain regions of the asphalt layer to be compacted are compacted more than others during a working operation. For example, it frequently occurs that the road roller operators pass over the edge areas of the asphalt layer less often than the areas in the middle. This results in an uneven compaction of the road and thus in a poorer quality of the finished road surface layer.
Several strategies are known in the prior art to ensure an optimal compaction of the asphalt layers. For example, systems are known in which it is possible by means of a global positioning system (GPS) to track with maximum precision which parts of the asphalt layer have already been compacted by the road rollers and which parts require further compaction. Systems are known in which the entire construction site is mapped in this manner and displayed to the operator of the road roller as a three-dimensional topography with different colors indicating areas with different degrees of compaction. In order to render a sufficiently precise positioning of the road roller possible, elaborate and expensive equipment is needed. U.S. Pat. No. 6,749,364 B1 discloses a system in which the road rollers are equipped with a thermal imaging camera which generates a thermal profile of the asphalt layer laid by the road paver and which displays the thermal profile to the road roller operator so that the latter knows where the asphalt layer currently has an optimal temperature for compaction. The rolling pattern is thus adapted here to the actual conditions in terms of the current temperature of the asphalt layer. In U.S. Pat. No. 6,749,364 B1, the position of the roller is also determined by means of GPS- or laser-based systems, e.g., calibrated total stations.
A disadvantage of the systems according to the prior art is that they require more elaborate technical equipment and involve increased acquisition costs and, in some cases, even increased operating costs. Moreover, when deviating from the planned rolling pattern as a result of the temperature profile of the asphalt layer, there is a risk that different areas will be compacted to different degrees.
An object of the present invention is thus to provide a method and a road roller with which the compaction process of an asphalt layer to be compacted in road construction is successfully monitored, so that the overall compaction quality can be improved. At the same time, the operator of the road roller is to be relieved of the burden of a rigorous monitoring of the adherence to the rolling pattern, so that he can concentrate on steering the road roller. Another object of the present invention is the successful monitoring of the compaction process with minimum technical expenditure and thus in a particularly cost-effective manner.